Pressurized reserve lubrication system for a gas turbine engine

ABSTRACT

A lubrication system includes a control subsystem operable to selectively communicate lubricant from a reserve lubrication subsystem under a pressure to supplement lubricant from a main lubrication subsystem in response to identification of a prolonged reduced-G condition. A gas turbine engine includes a main lubrication subsystem in communication with a geared architecture; a reserve lubrication subsystem in communication with the geared architecture; and a control subsystem operable to selectively communicate lubricant from the reserve lubrication subsystem under a pressure in response to identification of a prolonged reduced-G condition. A method of reducing lubrication starvation from a lubrication system with a main lubrication subsystem and a reserve lubrication subsystem, the main lubrication system in communication with a geared architecture of a gas turbine engine, includes communicating lubricant under a pressure to the geared architecture in response to identifying of a prolonged reduced-G condition.

This application is a continuation of U.S. patent application Ser. No.13/726,435 filed Dec. 24, 2012.

BACKGROUND

The present disclosure relates to a lubrication system for a gas turbineengine and, more particularly, to a lubrication system that remainsoperable in reduced gravity (reduced-G) conditions.

Aircraft gas turbine engines include a lubrication system to supplylubrication to various components. A reserve is also desirable to ensurethat at least some components are not starved of lubricant duringreduced-G conditions in which acceleration due to gravity is partiallyor entirely counteracted by aircraft maneuvers and/or orientation.

SUMMARY

A lubrication system according to one disclosed non-limiting embodimentof the present disclosure includes a main lubrication subsystem; areserve lubrication subsystem; and a control subsystem operable toselectively communicate lubricant from the reserve lubrication subsystemunder a pressure to supplement lubricant from the main lubricationsubsystem in response to identification of a prolonged reduced-Gcondition.

A further embodiment of the present disclosure includes, wherein thepressure is provided via a gas.

A further embodiment of the present disclosure includes, wherein the gasis an inert gas.

A further embodiment of the present disclosure includes, wherein thepressure is provided via a liquid.

A further embodiment of the present disclosure includes, wherein themain lubrication subsystem and the reserve lubrication subsystem are incommunication with a geared architecture of a gas turbine engine.

A further embodiment of the present disclosure includes, wherein thepressure provides lubricant to a journal pin of the geared architecturefrom the reserve lubrication subsystem to supplements lubricant from themain lubrication subsystem to the journal pin.

A further embodiment of the present disclosure includes a main lubricanttank solenoid valve in communication with the control subsystem and themain lubrication subsystem, the control subsystem is operable to closethe main lubricant tank solenoid valve in response to the prolongedreduced-G condition; and a reserve lubricant tank solenoid valve incommunication with the control subsystem, the control subsystem operableto open the reserve lubricant tank solenoid valve in response to theprolonged reduced-G condition.

A further embodiment of the present disclosure includes, wherein thecontrol subsystem operable to selectively communicate lubricant from thereserve lubrication subsystem under a pressure to supplement lubricantfrom the main lubrication subsystem in response to a sensor operable toidentify the prolonged reduced-G condition.

A gas turbine engine according to another disclosed non-limitingembodiment of the present disclosure includes a geared architecture; amain lubrication subsystem in communication with the gearedarchitecture; a reserve lubrication subsystem in communication with thegeared architecture; and a control subsystem operable to selectivelycommunicate lubricant from the reserve lubrication subsystem under apressure in response to identification of a prolonged reduced-Gcondition.

A further embodiment of the present disclosure includes, wherein thegeared architecture drives a fan at a lower speed than a low spool.

A further embodiment of the present disclosure includes, wherein thereserve lubrication subsystem includes a pressurized reserve lubricanttank that selectively communicates the lubricant.

A further embodiment of the present disclosure includes, wherein thepressurized reserve lubricant tank is within at least one of a nacelle,an engine pylori and an aircraft wing.

A further embodiment of the present disclosure includes a multiple ofpressurized reserve lubricant tanks.

A further embodiment of the present disclosure includes, wherein thepressurized reserve lubricant tank is pressurized via a gas.

A further embodiment of the present disclosure includes, wherein the gasis an inert gas.

A further embodiment of the present disclosure includes, wherein thepressurized reserve lubricant tank is pressurized via a liquid.

A method of reducing lubrication starvation from a lubrication systemwith a main lubrication subsystem and a reserve lubrication subsystem,the main lubrication system in communication with a geared architectureof a gas turbine engine, according to another disclosed non-limitingembodiment of the present disclosure includes communicating lubricantunder a pressure to the geared architecture in response to identifyingof a prolonged reduced-G condition.

A further embodiment of the present disclosure includes providing thepressure via a gas.

A further embodiment of the present disclosure includes providing thepressure via a liquid.

A further embodiment of the present disclosure includes communicatingthe lubricant under the pressure to a journal pin of the gearedarchitecture.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a schematic cross-section of a gas turbine engine;

FIG. 2 is a cross sectional side elevation view of a gear train usefulin an aircraft gas turbine engine;

FIG. 3 is a schematic diagram of a lubrication system;

FIG. 4 is a schematic diagram of a reserve lubricant tank of thelubrication system;

FIG. 5 is a block diagram of a control module that executes a reservelubricant supply logic;

FIG. 6 is a schematic diagram of a lubrication system according toanother disclosed non-limiting embodiment; and

FIG. 7 is a schematic diagram of a lubrication system according toanother disclosed non-limiting embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flowpath whilethe compressor section 24 drives air along a core flowpath forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan gas turbine engine in the disclosed non-limiting embodiment, itshould be understood that the concepts described herein are not limitedto use with turbofans as the teachings may be applied to other types ofturbine engines such as a three-spool (plus fan) engine wherein anintermediate spool includes an intermediate pressure compressor (IPC)between the LPC and HPC and an intermediate pressure turbine (IPT)between the HPT and LPT.

The engine 20 generally includes a low spool 30 and a high spool 32mounted for rotation about an engine central longitudinal axis Arelative to an engine static structure 36 via several bearing structures38. The low spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 (“LPC”) and a lowpressure turbine 46 (“LPT”). The inner shaft 40 drives the fan 42through a geared architecture 48 to drive the fan 42 at a lower speedthan the low spool 30.

The high spool 32 includes an outer shaft 50 that interconnects a highpressure compressor 52 (“HPC”) and high pressure turbine 54 (“HPT”). Acombustor 56 is arranged between the high pressure compressor 52 and thehigh pressure turbine 54. The inner shaft 40 and the outer shaft 50 areconcentric and rotate about the engine central longitudinal axis A whichis collinear with their longitudinal axes.

Core airflow is compressed by the low pressure compressor 44 then thehigh pressure compressor 52, mixed with the fuel and burned in thecombustor 56, then expanded over the high pressure turbine 54 and thelow pressure turbine 46. The turbines 54, 46 rotationally drive therespective low spool 30 and high spool 32 in response to the expansion.

In one non-limiting example, the gas turbine engine 20 is a high-bypassgeared architecture engine in which the bypass ratio is greater thanabout six (6:1). The geared architecture 48 can include an epicyclicgear train, such as a planetary gear system, star gear system or othergear system. The example epicyclic gear train has a gear reduction ratioof greater than about 2.3, and in another example is greater than about2.5. The geared turbofan enables operation of the low spool 30 at higherspeeds which can increase the operational efficiency of the low pressurecompressor 44 and low pressure turbine 46 and render increased pressurein a fewer number of stages.

A pressure ratio associated with the low pressure turbine 46 is pressuremeasured prior to the inlet of the low pressure turbine 46 as related tothe pressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle of the gas turbine engine 20. In one non-limitingembodiment, the bypass ratio of the gas turbine engine 20 is greaterthan about ten (10:1), the fan diameter is significantly larger thanthat of the low pressure compressor 44, and the low pressure turbine 46has a pressure ratio that is greater than about five (5:1). It should beunderstood, however, that the above parameters are only exemplary of oneembodiment of a geared architecture engine and that the presentdisclosure is applicable to other gas turbine engines including directdrive turbofans.

In one embodiment, a significant amount of thrust is provided by thebypass flow path due to the high bypass ratio. The fan section 22 of thegas turbine engine 20 is designed for a particular flightcondition—typically cruise at about 0.8 Mach and about 35,000 feet. Thisflight condition, with the gas turbine engine 20 at its best fuelconsumption, is also known as bucket cruise Thrust Specific FuelConsumption (TSFC). TSFC is an industry standard parameter of fuelconsumption per unit of thrust.

Fan Pressure Ratio is the pressure ratio across a blade of the fansection 22 without the use of a Fan Exit Guide Vane system. The low FanPressure Ratio according to one non-limiting embodiment of the examplegas turbine engine 20 is less than 1.45. Low Corrected Fan Tip Speed isthe actual fan tip speed divided by an industry standard temperaturecorrection of (“T”/518.7)^(0.5). in which “T” represents the ambienttemperature in degrees Rankine. The Low Corrected Fan Tip Speedaccording to one non-limiting embodiment of the example gas turbineengine 20 is less than about 1150 fps (351 m/s).

With reference to FIG. 2, the geared architecture 48 includes a sun gear60 driven by a sun gear input shaft 62 from the low speed spool 30, aring gear 64 connected to a ring gear output shaft 66 to drive the fan42 and a set of intermediate gears 68 in meshing engagement with the sungear 60 and ring gear 64. Each intermediate gear 68 is mounted about ajournal pin 70 which are each respectively supported by a carrier 74. Areplenishable film of lubricant, not shown, is supplied to an annularspace 72 between each intermediate gear 68 and the respective journalpin 70.

A lubricant recovery gutter 76 is located around the ring gear 64. Thelubricant recovery gutter 76 may be radially arranged with respect tothe engine central longitudinal axis A. Lubricant is supplied thru thecarrier 74 and into each journal pin 70 to lubricate and cool the gears60, 64, 68 of the geared architecture 48. Once communicated through thegeared architecture the lubricant is radially expelled thru thelubricant recovery gutter 76 in the ring gear 64 by various paths suchas lubricant passage 78.

The input shaft 62 and the output shaft 66 counter-rotate as the sungear 60 and the ring gear 64 are rotatable about the engine centrallongitudinal axis A. The carrier 74 is grounded and non-rotatable eventhough the individual intermediate gears 68 are each rotatable abouttheir respective axes 80. Such a system may be referred to as a starsystem. It should be appreciated that various alternative and additionalconfigurations of gear trains such as planetary systems may also benefitherefrom.

Many gear train components readily tolerate lubricant starvation forvarious intervals of time, however, the journal pins 70 may berelatively less tolerant of lubricant starvation. Accordingly, whetherthe gear system is configured as a star, a planetary or otherrelationship, it is desirable to ensure that lubricant flows to thejournal pins 70, at least temporarily under all conditions inclusive ofreduced-G conditions which may arise from aircraft maneuvers and/oraircraft orientation. As defined herein, reduced-G conditions includenegative-G, zero-G, and positive-G conditions materially less than 9.8meters/sec./sec. (32 feet/sec./sec.).

With Reference to FIG. 3, a lubrication system 80 is schematicallyillustrated in block diagram form for the geared architecture 48 as wellas other components 84 (illustrated schematically) which may requirelubrication. It should be appreciated that the lubrication system 80 isbut a schematic illustration and is simplified in comparison to anactual lubrication system. The lubrication system 80 generally includesa main lubrication subsystem 86, a reserve lubrication subsystem 88 anda control subsystem 90.

The main lubrication subsystem 86 generally includes a main lubricanttank 92 which is a source of lubricant to the geared architecture 48. Itshould be understood that although not shown, the main lubricationsubsystem 86 may include numerous other components such as a sump,scavenge pump, main pump and various lubricant reconditioning componentssuch as chip detectors, heat exchangers and deaerators, which need notbe described in detail herein.

The reserve lubrication subsystem 88 generally includes a pressurizedreserve lubricant tank 94 and may also include numerous other componentswhich need not be described in detail herein. The pressurized reservelubricant tank 94 may be located remote from the main lubricant tank 92such as, for example, within the engine nacelle 96, an engine pylon 98or wing 100 (FIG. 4). It should be appreciated that the pressurizedreserve lubricant tank 94 may provide less lubricant volume than themain lubricant tank 92. In one disclosed non-limiting embodiment, thepressurized reserve lubricant tank 94 may provide approximately fiftypercent (50%) of the volume of the main lubricant tank 92. In anotherdisclosed non-limiting embodiment, the pressurized reserve lubricanttank 94 may sized to provide lubricant only to specific components suchas the journal pins 70.

The pressurized reserve lubricant tank 94 may be pressurized with aninert gas such as nitrogen. A flexible barrier 102 may be located toseparate the nitrogen from the lubricant to prevent intermixturethereof. It should be appreciated that other pressurization systems suchas a separate pressure source, or other flexible barrier arrangement mayalternatively or additionally be provided.

The control subsystem 90 generally includes a control module 104 thatexecutes a reserve lubricant supply logic 106 (FIG. 4). The functions ofthe logic 106 are disclosed in terms of functional block diagrams, andit should be understood by those skilled in the art with the benefit ofthis disclosure that these functions may be enacted in either dedicatedhardware circuitry or programmed software routines capable of executionin a microprocessor based electronics control embodiment. In onenon-limiting embodiment, the control module 104 may be a portion of aflight control computer, a portion of a Full Authority Digital EngineControl (FADEC), a stand-alone unit or other system.

The control module 104 typically includes a processor 104A, a memory104B, and an interface 104C. The processor 104A may be any type of knownmicroprocessor having desired performance characteristics. The memory104B may be any computer readable medium which stores data and controlalgorithms such as logic 106 as described herein. The interface 104Cfacilitates communication with other components such as an accelerometer108A, a main lubricant tank valve 110 and a reserve lubricant tank valve112. It should be appreciated that various other components such assensors, actuators and other subsystems may be utilized herewith.

The lubrication system 80 is operable in both normal G-operation andreduced-G operation. During normal G-operation, the main lubricant tank92 operates as the source of lubricant to the geared architecture 48.Although effective during normal-G operation, it may be desirable toextend such operability to reduced-G operation to assure that the gearedarchitecture 48 will always receive an effective lubrication supplyirrespective of the lubrication pump (not shown) being unable togenerate proper pressure.

Under reduced-G operation, the accelerometer 108A will sense thiscondition and communicate same to the control module 104. The reservelubricant supply logic 106 (FIG. 5) will then be identify whether aprolonged reduced-G condition exists. A “prolonged reduced-G condition”is defined herein as a condition that lasts a length of time greaterthan a transient condition during which G forces are below gravity,e.g., 1G. In one disclosed non-limiting embodiment, the reservelubricant supply logic 106 identifies a specific continuous time periodduring which the engine 20 is subject to the reduced-G condition suchas, for example only, seven (7) seconds. It should be appreciated thatother time periods as well as additional or alternative conditions maybe utilized to further refine the logic.

After the predetermined time period, the reserve lubricant supply logic106 closes the main lubricant tank valve 110 and opens the reservelubricant tank valve 112. The main lubricant tank valve 110 is therebyisolated and the pressurized reserve lubricant tank 94 provideslubricant under gas pressure to the geared architecture 48 irrespectiveof the reduced-G condition. The geared architecture 48 is therebyassured an effective lubrication supply.

After the reduced-G condition passes, the main lubricant tank valve 110is opened to again supply lubricant to the geared architecture 48. Thereserve lubricant tank valve 112 may remain open as even if too muchlubricant is then supplied, the excess lubricant can escape via anoverflow vent 114. That is, the additional lubricant is cycled throughthe system or otherwise removed therefrom.

With reference to FIG. 6, another disclosed non-limiting embodiment of alubrication system 80′ alternatively or additionally includes othersensors such as a lubricant flow sensor 116. The flow sensor 116communicates with the control module 104 to identify a prolongedreduced-G condition through identification of a reduced flow oflubricant to the geared architecture 48. That is, the flow sensor 116identifies a below desired lubricant flow to the geared architectureirrespective of the G forces. It should be appreciated that flow sensor116 may be used in addition or in the alternative to the accelerometer108.

With reference to FIG. 7, another disclosed non-limiting embodiment of alubrication system 80″ provides a multi-shot system in which a multipleof pressurized reserve lubricant tanks 94A, 94B, . . . , 94 ncommunicate with the geared architecture 48 through respective solenoidvalves 112A, 112B, . . . , 112 n. The solenoid valves 112A, 112B, . . ., 112 n are respectively actuated as described above to provide amulti-shot system which may be sequentially activated should multiplereduced-G conditions occur.

Once used, the empty pressurized reserve lubricant tank(s) are thenreplaced or recharged in a maintenance operation once the aircraft haslanded. For example, the pressurized reserve lubricant tank 94 mayessentially be a line-replaceable unit that need only be plugged intothe lubricant system for replacement. Furthermore, as the pressurizedreserve lubricant tank 94 may be located in various locations (FIG. 4),maintenance access is readily achieved.

It should be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” “bottom”, “top”,and the like are with reference to the normal operational attitude ofthe vehicle and should not be considered otherwise limiting.

It should be understood that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed is:
 1. A lubrication system, comprising: a main lubrication subsystem; a reserve lubrication subsystem; and a control subsystem operable to selectively communicate lubricant from said reserve lubrication subsystem under a pressure to supplement lubricant from said main lubrication subsystem in response to identification of a prolonged reduced-G condition.
 2. The lubrication system as recited in claim 1, wherein said pressure is provided via a gas.
 3. The lubrication system as recited in claim 2, wherein said gas is an inert gas.
 4. The lubrication system as recited in claim 1, wherein said pressure is provided via a liquid.
 5. The lubrication system as recited in claim 1, wherein said main lubrication subsystem and said reserve lubrication subsystem are in communication with a geared architecture of a gas turbine engine.
 6. The method as recited in claim 5, wherein said pressure provides lubricant to a journal pin of the geared architecture from said reserve lubrication subsystem to supplement lubricant from said main lubrication subsystem to the journal pin.
 7. The lubrication system as recited in claim 1, further comprising: a main lubricant tank solenoid valve in communication with said control subsystem and said main lubrication subsystem, said control subsystem is operable to close said main lubricant tank solenoid valve in response to the prolonged reduced-G condition; and a reserve lubricant tank solenoid valve in communication with said control subsystem, said control subsystem operable to open said reserve lubricant tank solenoid valve in response to the prolonged reduced-G condition.
 8. The lubrication system as recited in claim 1, wherein said control subsystem operable to selectively communicate lubricant from said reserve lubrication subsystem under a pressure to supplement lubricant from said main lubrication subsystem in response to a sensor operable to identify the prolonged reduced-G condition.
 9. A gas turbine engine, comprising: a geared architecture; a main lubrication subsystem in communication with said geared architecture; a reserve lubrication subsystem in communication with said geared architecture; and a control subsystem operable to selectively communicate lubricant from said reserve lubrication subsystem under a pressure in response to identification of a prolonged reduced-G condition; wherein said reserve lubrication subsystem includes a pressurized reserve lubricant tank that selectively communicates the lubricant.
 10. The gas turbine engine as recited in claim 9, wherein said geared architecture drives a fan at a lower speed than a low spool.
 11. The gas turbine engine as recited in claim 9, wherein said pressurized reserve lubricant tank is within at least one of a nacelle, an engine pylori and an aircraft wing.
 12. The gas turbine engine as recited in claim 9, further comprising a multiple of pressurized reserve lubricant tanks.
 13. The gas turbine engine as recited in claim 9, wherein said pressurized reserve lubricant tank is pressurized via a gas.
 14. The gas turbine engine as recited in claim 13, wherein said gas is an inert gas.
 15. The gas turbine engine as recited in claim 9, wherein said pressurized reserve lubricant tank is pressurized via a liquid.
 16. A method of reducing lubrication starvation from a lubrication system with a main lubrication subsystem and a reserve lubrication subsystem, the main lubrication system in communication with a geared architecture of a gas turbine engine comprising: communicating lubricant under a pressure to the geared architecture in response to identifying a prolonged reduced-G condition.
 17. The method as recited in claim 16, further comprising: providing the pressure via a gas.
 18. The method as recited in claim 16, further comprising: providing the pressure via a liquid.
 19. The method as recited in claim 16, further comprising: communicating the lubricant under the pressure to a journal pin of the geared architecture. 